Water chemistry may significantly affect sorption extent by
altering the charges of graphene surfaces or organic molecules
and therefore modifying electrostatic interactions. An approximately
twofold increase (for cationic molecules) or decrease (for
anionic molecules) in sorption extent could be possible for negatively-charged
graphene oxide within the typical pH limits (about
6–10) of natural and treated water. The oxygen impurity contents
(responsible for surface functional group acidity) among graphene
powders should therefore be considered along with the charges of
the organic compounds targeted for removal. We hypothesize that
graphene surface charge could be modified through doping of element
impurities or charged functional groups in order to manipulate
sorption extent for particular compounds. Promotion of
phenolic content may be helpful as well.